Kohei Uchimura's bid to become the first gymnast in more than 40-years to win back-to-back Olympic all-around golds began with a costly error as his as addiction to Pokemon Go resulted in a phone bill of nearly $5,000.

Uchimura, 27, who has won a record six successive world all-around titles, was persuaded by his team mates to download the game shortly after touching down in Sao Paulo for a pre-games training camp last week.

But rather than getting a buzz by playing a game that has turned into a global craze over the past weeks, Uchimura was left with a mighty headache when he saw his bill, the result of using a lot of data while roaming.

"500,000 yen ($4,940)," a red-faced Uchimura told Kyodo News.

Teammate Kenzo Shirai added: "He looked dead at the team meal that day."

The bill capped a frustrating few days for Uchimura: He is unlikely to have made any captures in the game, because it is not officially available in Brazil.

However, such is Uchimura's standing in his homeland that his mobile phone company agreed to waive the bulk of the cost after he explained his mistake — and instead implemented a flat-rate roaming charge of about $30 a day.

"I really lucked out," said Uchimura, who blocked out his obsession of chasing after virtual reality monsters as he went through his paces during a training session with his Japanese teammates in the Rio Olympic Arena on Wednesday.